1. Field of the Invention
This invention relates to formulations that are blood compatible and shear sensitive. More particularly, such formulations comprising a high density, polymer in combination with a density reducing component are particularly useful for facilitating the separation of blood serum or plasma from the cellular portion of blood.
2. Description of the Related Art
Biochemical tests carded out in a clinical laboratory require use of blood serum or plasma as a sample. For preparing the sample for examination, it is frequently necessary to separate the blood serum or plasma from the solid blood components. There are various types of blood separating compositions which are used to separate the blood components from one another. In particular, serum separators are dispersions consisting of hydrophobic polymers and additives to regulate density and rheology. Typical separators contain low density polymers such as polyesters with silica thickeners which increase the density and form the required flow properties. The main ingredient in such compositions, is a polymer.
U.S. Pat. Nos. 3,780,935, 3,920,549, 3,997,442 and 4,148,764 for example, disclose polyester compositions that exhibit thixotropic like properties. In particular, U.S. Pat. No. 5,124,434 discloses a composition that also exhibits thixotropic properties comprising a polyester with a density of 1.01 to 1.09, comprising one mole of a dicarboxylic acid member and one mole of a diol member wherein said acid member is comprised of a first dicarboxylic acid component having from about 5 to about 60 mole percent of an aliphatic dicarboxylic acid having from 13 to about 22 carbon atoms, a second dicarboxylic acid component having from about 35 to about 90 mole percent of an aliphatic dicarboxylic acid having from 4 to about 12 carbon atoms, a third dicarboxylic acid component having from about 5 to about 25 mole percent of an aliphatic dicarboxylic acid having about 36 carbon atoms.
Whereas there are numerous publications related to compositions useful for facilitating the separation of blood serum of plasma from the cellular portion of blood, there are no publications that suggest or teach polymers with a high density combined with a density reducing component to yield blood compatible and shear sensitive gel formulations.